Whitney's extension problem for Cm

Charles Fefferman
2006 Annals of Mathematics  
Let f be a real-valued function on a compact set in R n , and let m be a positive integer. We show how to decide whether f extends to a C m function on R n .
doi:10.4007/annals.2006.164.313 fatcat:4xkjwdg3mjh6njr4qm3tnpdomm